New heat flow data from south-eastern South Australia

Abstract

Heat flow has been measured in south-east South Australia at a spatial resolution greater than previously available. The study area contains the Southern Murray Basin, Padthaway Ridge, and Western Otway Basin. An extensive network of groundwater observation wells across the study area was used, along with several petroleum wells in the Otway Basin, to measure thermal gradients and calculate 24 new heat flow values.Geothermal gradients were either measured directly using a cable, winch, and thermistor in cased or open holes with standing water, or by estimating average geothermal gradients from petroleum well completion temperature data. Thermal conductivity values were measured directly on existing core samples using a divided bar apparatus.A map constructed from the measured values reveals a heat flow dataset that is non-uniform and variable over relatively short distances. Measured heat flow values range between 42 and 123 mW/m–2. In particular, a 40 km long, 15 km wide zone of elevated heat flow is identified along the northern margin of the Otway or Gambier Sub-basin that may correspond to the occurrence of Delamerian granitoids units of the Padthaway Ridge. High-resolution surface heat flow mapping provides valuable data for further research into the tectonothermal evolution of south-east Australia.